1. Field of the Invention
This invention relates to a pattern recognition apparatus, and more particularly to a pattern recognition apparatus having a registration mode in which a pattern used as a recognition reference is registered.
2. Description of the Related Art
FIG. 1 shows an example of a conventional speech recognition system designed for a small number of non-specified speakers. The speech recognition system includes a speech pattern detection section 1 for frequency-analyzing input speech and for detecting a characteristic speech pattern thereof, and a pattern recognition apparatus 2 for recognizing the speech pattern input from the speech pattern detection section. The pattern recognition apparatus 2 includes a pattern memory section 3 for storing a plurality of reference patterns, a comparing section 4 for recognizing the speech pattern from the speech pattern detection section 1 based on the similarity between the speech pattern and each of the reference patterns stored in the pattern memory section 3, and a switch for selectively connecting the speech pattern detection section 1 to one of the pattern memory section 3 and the comparing section 4.
In the registration mode, a speech pattern is supplied from the speech pattern detector 1 to the pattern memory section 3 via the switch and registered into the pattern memory as a recognition pattern. On the other hand, in the recognition mode, a speech pattern is supplied from the speech pattern detector 1 to the comparing section 4 via the switch and then compared with a plurality of reference patterns registered in the pattern memory section 3.
In a case where a plurality of speech patterns of a specified speaker are registered as recognition patterns in the pattern memory, it becomes difficult to attain a high rate of pattern recognition for a non-specified speaker. If additional recognition patterns are registered into the pattern memory section 3 and consequently the number of speech patterns to be recognized is increased, the difference between the reference patterns becomes small so that the pattern recognition rate may be lowered. For this reason, the recognition operation is effected in the recognition mode by using reference patterns registered in the pattern memory section 3 and some of the reference patterns are modified to correctly recognize speech patterns which are difficult to recognize, thus enhancing the recognition rate.
However, modification of the reference patterns cannot be always effected with good results, and sometimes the recognition rate may become lower than that which may be obtained without modification. In the conventional speech recognition system, a new speech pattern is written over the reference pattern which requires modification and the reference pattern is removed from the pattern memory. Therefore, if the modification is made in fail, the content of the pattern memory section cannot be returned to the state prior to the modification. For example, substantially the same reference pattern as that obtained before the modification can be registered into the pattern memory section by inputting a speech to the speech pattern detection section, but this needs a long time and much labor.